Lubricant testing method and apparatus



W 3 11944. A.' L. M. A. ROUY LUBRICAN'I" TESTING METHOD AND APPARATUS Filed Aug. 30, 1941 4 Sheets-Sheet l May 23; 3944? A. 1 M. A. ROUY 2,349,563

LUBRICANT TESTINGMETHOD AND APPARATUS Filed Aug. 30, 1941 4 Sheets-Sheet 2 lil 1 @l Maly 23, 1944. A. L M. A. ROUY LUBRICANT TESTING METHOD AND APPARATUS Filed Aug. 30, 1941 4 Sheets-Sheet 3 ay 23, 1944. A. l.. M. A. ROUY LUBRICANT TESTING METHOD AND APPARATUS Filed Aug. 30, 1941 4 Sheets-Sheet 4 nnnnnnnnnnnbnnwnwn DDDDDEEDDUDDDDDDDDD Patented May 23, i944 tunisienne rus'rnyo Mn'rnonann .erroneous Auguste Louis Marie Antoine Iitouy, New AYork,

N. Y., assigner to The Gyro-Baiance Corporation, Greenwich, Conn., a corporation of Delawill@ Application August 3ft, 1.941, Serial No. 409,079-

(ci. zes-io) i @la-inns.

The invention relates to a method and `apparai-.us for testing lubricants, especiallyelubricating oiis. the coefificient of friction and the lm forming properties of oils used in the bearings of rotating sila-its. l,

lihe primary object of the invention is to pro-A vide an accurate method and apparatus for measuring the frictional properties of a lubricant.

Another objectof the invention is to provide It is especially directed to discovering a method lof this nature which is quick and simj plef, and, therefore, economical.

Still another purpose is to provide a method for selecting, for a. bearing and shaft of given characteristics, the lubricant bestsuited for such bearing and shaft.

an additional object of the invention is to provide a procedure for determining the angular velocity at which, with a given hearing and shaft, any selected lubricant will forni a continuous iiiin, or will attain proper lubricating conditions.

Still a further'purpose of the invention is to balanced shaft which isubricated by the material tobe tested, and measuring instantaneously the variations in the forces acting on the shaft. From these forces the coefficient of friction under varying conditions can be determined.

Further objects and advantages will be seen from the following description when taken in conjunction with the accompanying drawings, which form a part thereof.

In the drawings:

Fig. 1 shows dia'grammatically an apparatus for use in carrying out the invention.

Figure lA is a diagramma-tic view in' elevation of one end of the apparatus showing a, driving means. i

Figs. 2 and 3 are sections at ,right angles to one another through the shaft mounting and force detecting portions thereof.`

Fig. 4 is a diagram of the forces developed on the shaft and bearing.

Figs. 5 and 6 are diagrams of types of patterns which ,form

onthe screen of the cathode ray tube.

Figs. 7 and 8 are diagrams used in explaining I the invention.

the process is shown in Figs. 1 to 3 and is described in more detail in my prior application S. N. 266,714, rlled April 7, 1939, which has matured as United States Patent No. 2,329,654, Septomber le, 1943.

A shaft 2 of a rotor i is mounted at its ends, in bearings such .as ii (see Figs. 2 and 3). These bearings t in notches t formed in a support it. This support is connectedA to the frame i2 of `the machine by a portion it, which is vertically *iicxible but is so constructed and arranged that lateral movement of the shaft with respect to the frame is prevented.

The rotor shaft 2 is driven by any suitable means such as, for example, that illustrated in Fig. 1A. of the drawings. is coupled to a driving motor lvl by means of any type oi exible coupling designed to prevent the transmission of stray oscillations to the shaft,

and the speed of the motor may be regulated by means of the rheostat R. The speed of the motor may be determined at any time by means Yof a suitable tachometer T Support iii has in its bottom wall a seat for the upper end of a pin it, pointed at both its ends. The lower end of thispin rests in a seat in a exible diaphragm l which rests on a piezoelectric crystal fb, formed of' a layer of quartz 'between two iron plates. This crystal in turn rests on a support 22 rigid with frame i2. As all the parts are substantially incompressible, the

support i@ for the shaft is eifectively prevented from moving downwardly to any measurable extent with respect to the frame, but all forces exerted thereon are transmitted to the piezo- Current is supplied to the shaft 2 from a highv voltagesource through the network indicated at the lefthand end of Figure 1. At each revolution, when electrode 24 moves close to an electrode `26, this current jumps to electrode 26 and In this gure the shaft thence, through a suitable circuit including transformer 32, energizes the vertical plates 34 of a cathode ray tube, so as to cause the ray of this tube4 to move horizontally across the screen 36.

Piezoelectric crystal 20 is connected through an amplifying `system tothe horizontal plates 38' of the same cathode ray tube, so that a force exerted by the shaft causes vertical deviation of the ray thereof. i yAs described in my prior patent above referredto, this mechanism is used for determining the unbalance of a shaft. As so used, there is obtained on the screen 36 a vertical line and one ormore horizontal lines, forming a sort of H. This results from the fact that the unbalance force is'synchronized with the rotation of the shaft so that, for any given position of electrodes` 26, the transverse impulse produced thereby occurs at the same point in thevertical movement;

J a lemniscate. Since the areas on opposite sides of the center are.nearly equal, and since these areas are of opposite sign,l their rdierence is very small and indicates that the frictlonal force and therefore the coeicient of friction are very low. In other words, a satisfactory lubricant for the particular type of shaft and bearing has been found.

The invention may be used to indicate very exactly the angular speed at which the oil forms va continuous film.v At low speeds., the oil film is e not continuous and friction .is high.` By gradu- A shaft 2 which has been corrected for accu@` I Referring now to Fig. 4, the friction .f the oil layer 40 causes the shaft 2 to .exert on the bearing 6 a force F which is horizontally directed through the lowest point p of the shaft 2. 'I'his force may be resolved into two components, one f2 directed along a line joining point p with the center of iiexion o of the exible member I4, which is the, point about which the bearing tends to move.

under the action of force F, this line forming an angle a with the horizontal; and a.vertical vforce fl. F'orcefZ is rendered ineffective' by the mounting of the shaft, While force fl is transmitted by pin I6 to the piezoelectric element 20.

Thus, variations in the force fl cause variations in the energization of thehorizontal plates 38 of the cathode -ray tube, and will produce deviations of the beam thereof.y

By applying a force of known value along the 1 `line of`fcrce F, and noting the resulting reading von the screen of the tube, the deviation caused `by a given force can be determined.' From this,

the value of the friction and thereby the coeiil- 'cient of friction can be found.

The same result can be obtained by determining the vertical force fl, by suitable calibration of the instrument controlled by the piezoelectric crystal 20, and multiplying this value by the co tangent of `angle q, this angle being constant in any given test because of .the rigid support of carrier :I by pin I 6. f

Because the force produced by the friction is continuous, though somewhat variable (and not periodically reversed in synchronism-with the rotation of the shaft, as in the case of an unbalancing mass), they pattern resulting Aon the screen will take a form generally similar to one of those shown in Figs. 5 and '6. In Fig. 5, the frictional forces are high and a pattern enclosed by the line 42 results. portional to the average friction. With a better lubricant, on the other hand, a pattern such as 44 of Fig. 6 is obtained, generally in the form of ally increasing the speed of a balanced shaft in theymanner discussed above, and plotting the force f against the angular speed w, a curve c such as that shown in Fig. 7 is obtained. It will be noted that the force is high at the beginning, rapidly drops to the point M, and then slowly increases. The shaded portion of the curve represents the dangerous speeds at which no oil film is present, and point M shows the angular speed w' at which the oil lm is formed.

Measurements of the frictional forces which arise when a shaft stops are also possible. As shown in Fig. 8, in which the force is plotted as the ordinate against time t, during the period dt, beginning at point "at, when the shaft is slowing down from a speed at which the average frictional force had been F, the force of friction fluctuates rapidly While reversing its direction until the shaft stops at point x. The value A of the maximum iiuctuationis an indication of the lubricating properties of the oil, and is smaller as 'the oil is better.

Fig. 9 shows a modiedform of apparatus for carrying o'ut the invention. The cathode ray tube by plates 38 directs its ray on a moving sensitive film 50, thus tracing thereon a line 52. The filmvis synchronized with the rotation of the shaft, so that the deviations" produced by the frictional force can be measured.

Fig. 10 shows still another apparatus in which the currents generated by piezoelectric crystal 20 are amplified by a suitable circuit and fed to a milliammeter 54, the readings of which vary proportionately to the force of friction.

e The method is equally applicable to other types of' bearings, such as ball j bearings or roller bearings. r

' As employed in thepresent specification and' claims, 4the terms "balanced shaft, .balanced rotor or the like are intended to designate masses The area of this pattern is prowhich have been placed in accurate balance and tested as by means of the device described in the applicants copending application to which refer ence has already been^made. The terms also have especial reference to such masses from which all dynamic unbalance has been eliminated.

While I have described herein some embodiments, I wish it tc be understood that Ido not intend to limit myself thereby, except within the y scope of the appended claims.

I claim:

1. A method of measuring the lubricating characteristics of a lubricant, which comprises applying the lubricant between a bearing and a bal-v anced shaft supported therein, starting the rotation of the shaft and gradually increasing the angular speed thereof, measuring during such starting and -rotation the force of friction caused by 'rotation of the shaft and measuring the speed of rotation at each measurement of force, to determine the angular speed at which such force is least and thereby the angular speed at which ing and shaft,

2. A method of measuring the lubricating characteristics of a lubricant, which comprises supporting a substantially perfectly balanced rotor in a bearing, applying the lubricant between the bearing and the balanced rotor, applying power to said rotor to rotate the same, cutting oi said power and allowing said rotor to freely decelerate, and measuring the uctuations of frictional forces set up in the bearing during the period of deceleration.

3. Apparatus for testing the lubricating properties of lubricants which comprises, in lcombination, a frame, bearings mounted on said frame, a balanced rotor supported for rotation in 'said bearings, me'ans for driving said rotor, the relatively rotating surfaces of said rotor and said bearing constituting housing means for the lubricant being tested, a mechano-electric transducer operatively connected with at least one of said bearings and subject to at least a proportional part of the stresses set up in 'said bearings by rotation of the rotor therein, and indicating means actuated by said transducer for yieldingameasure of the forces of friction between the relatively rotating rotor and bearing surfaces.

tion, a frame, a bearing member connected with said frame by a substantially horizontally ex tending arm which is subject to slight exure, a balanced rotor supported in said bearing member, means for driving said rotor, the relatively rotating surfaces of said rotor and said bearing member constituting a housing for the lubricant being tested, a supporting structure for said bear- -ing member disposed beneath'the latter, a mesaid frame by a substantially horizontally extend- 4. Apparatus for testing the lubricating properties of lubricants which comprises, in combina; tion, a frame, a bearing member, a balanced rotor supported in said bearing member, means for driving said rotor, the relatively rotating surfaces of said rotor and said bearing member constituting a housing for' the lubricant being tested,

tween said rotor and'said bearing member, and

indicating means operatively connected with said transducer yielding a measure of said forces.

5. Apparatus for testingtne lubricating properties of lubricants which' comprises, in combina ing arm which is subject to slight nexure, a balanced rotor supported in said bearing member, means for 'driving said rotor, the relatively rotating surfaces or" said rotor and s'aid bearing member constituting a housing for the lubricant being tested, a substantially rigid supporting structure for said bearing member disposed beneath the latter, a substantially incompressible mechano-electric transducerforming a part of said supporting structure and comprising a piezoelectric crystal and means actuated by said transducer to indicate the magnitude of the frictional forces between said rotor and bearing surfaces.

7. A method of measuring the lubricating characteristics of a lubricant which comprises horizontally supporting a substantially perfectly balanced rotor in a bearing against movement in any radial direction except microscopic movement in the direction of one radius of the rotor,

lubricating the contacting surfaces of the rotor and bearing with the iubricant to be tested, rotating said rotor, and' measuring the component of the irictional forces produced upon said bearing `by the rotation of said rotor, which component has a direction substantially parallel with said radius. 

